backend: add ManualReconnect method and call on iOS

When the iOS app goes into the background, its TCP
connections (Electrum server connetions) are killed after a
while (~30s).

When the user goes back into the app, we want to immediatelly trigger
a reconnect, not waiting for the regular 30s reconnect timer.

```
go get github.com/BitBoxSwiss/block-client-go@924dde9
go mod tidy
go mod vendor
```

backend/backend.go

@@ -538,6 +538,43 @@ func (backend *Backend) Coin(code coinpkg.Code) (coinpkg.Coin, error) {
 	return coin, nil
 }
 
+// ManualReconnect triggers reconnecting to Electrum servers if their connection is down.
+// Only coin connections that were previously established are reconnected.
+// Calling this is a no-op for coins that are already connected.
+func (backend *Backend) ManualReconnect() {
+	var electrumCoinCodes []coinpkg.Code
+	if backend.arguments.Testing() {
+		electrumCoinCodes = []coinpkg.Code{
+			coinpkg.CodeTBTC,
+			coinpkg.CodeTLTC,
+		}
+	} else {
+		electrumCoinCodes = []coinpkg.Code{
+			coinpkg.CodeBTC,
+			coinpkg.CodeLTC,
+		}
+	}
+	backend.log.Info("Manually reconnecting")
+	for _, code := range electrumCoinCodes {
+		c, err := backend.Coin(code)
+		if err != nil {
+			backend.log.WithError(err).Errorf("could not find coin: %s", code)
+			continue
+		}
+		btcCoin, ok := c.(*btc.Coin)
+		if !ok {
+			backend.log.Errorf("Expected %s to be a btc coin", code)
+			continue
+		}
+		blockchain := btcCoin.Blockchain()
+		if blockchain == nil {
+			// Not initialized yet
+			continue
+		}
+		blockchain.ManualReconnect()
+	}
+}
+
 // Testing returns whether this backend is for testing only.
 func (backend *Backend) Testing() bool {
 	return backend.arguments.Testing()

backend/bridgecommon/bridgecommon.go

@@ -166,6 +166,18 @@ func UsingMobileDataChanged() {
 	})
 }
 
+// ManualReconnect exposes the ManualReconnect backend method.
+func ManualReconnect() {
+	mu.RLock()
+	defer mu.RUnlock()
+
+	if globalBackend == nil {
+		return
+	}
+	globalBackend.ManualReconnect()
+
+}
+
 // BackendEnvironment implements backend.Environment.
 type BackendEnvironment struct {
 	NotifyUserFunc      func(string)

backend/coins/btc/blockchain/blockchain.go

@@ -118,4 +118,5 @@ type Interface interface {
 	Close()
 	ConnectionError() error
 	RegisterOnConnectionErrorChangedEvent(func(error))
+	ManualReconnect()
 }

backend/coins/btc/blockchain/mocks/mock.go

@@ -39,6 +39,7 @@ type BlockchainMock struct {
 	MockConnectionError      func() error
 
 	MockRegisterOnConnectionErrorChangedEvent func(func(error))
+	MockManualReconnect                       func()
 }
 
 // ScriptHashGetHistory implements Interface.
@@ -135,3 +136,10 @@ func (b *BlockchainMock) RegisterOnConnectionErrorChangedEvent(f func(error)) {
 		b.MockRegisterOnConnectionErrorChangedEvent(f)
 	}
 }
+
+// ManualReconnect implements Interface.
+func (b *BlockchainMock) ManualReconnect() {
+	if b.MockManualReconnect != nil {
+		b.MockManualReconnect()
+	}
+}

backend/coins/btc/electrum/failoverclient.go

@@ -156,6 +156,10 @@ func (f *failoverClient) TransactionGet(txHash chainhash.Hash) (*wire.MsgTx, err
 	})
 }
 
+func (f *failoverClient) ManualReconnect() {
+	f.failover.ManualReconnect()
+}
+
 func (f *failoverClient) Close() {
 	f.failover.Close()
 }

backend/mobileserver/mobileserver.go

@@ -227,8 +227,13 @@ func CancelAuth() {
 	bridgecommon.CancelAuth()
 }
 
-// AuthResult triggers an auth feeedback notification (auth-ok/auth-err) towards the frontend,
+// AuthResult triggers an auth feedback notification (auth-ok/auth-err) towards the frontend,
 // depending on the input value.
 func AuthResult(ok bool) {
 	bridgecommon.AuthResult(ok)
 }
+
+// ManualReconnect wraps bridgecommon.ManualReconnect.
+func ManualReconnect() {
+	bridgecommon.ManualReconnect()
+}

frontends/ios/BitBoxApp/BitBoxApp/BitBoxAppApp.swift

@@ -91,24 +91,23 @@ class GoEnvironment: NSObject, MobileserverGoEnvironmentInterfaceProtocol {
 
 class GoAPI: NSObject, MobileserverGoAPIInterfaceProtocol, SetMessageHandlersProtocol {
     var handlers: MessageHandlersProtocol?
-    
+
     func pushNotify(_ msg: String?) {
         self.handlers?.pushNotificationHandler(msg: msg!)
     }
 
     func respond(_ queryID: Int, response: String?) {
         self.handlers?.callResponseHandler(queryID: queryID, response: response!)
     }
-    
+
     func setMessageHandlers(handlers: MessageHandlersProtocol) {
         self.handlers = handlers
     }
 }
 
-
 @main
 struct BitBoxAppApp: App {
-   var body: some Scene {
+    var body: some Scene {
         WindowGroup {
             GridLayout(alignment: .leading) {
                 let goAPI = GoAPI()
@@ -118,12 +117,13 @@ struct BitBoxAppApp: App {
                         setupGoAPI(goAPI: goAPI)
                     }
                     .onReceive(NotificationCenter.default.publisher(for: UIApplication.willEnterForegroundNotification)) { _ in
-                            MobileserverTriggerAuth()
+                        MobileserverManualReconnect()
+                        MobileserverTriggerAuth()
                     }
             }
         }
     }
-    
+
     func setupGoAPI(goAPI: MobileserverGoAPIInterfaceProtocol) {
         let appSupportDirectory = FileManager.default.urls(for: .applicationSupportDirectory, in: .userDomainMask).first!
         do {

go.mod

@@ -4,7 +4,7 @@ go 1.22
 
 require (
 	github.com/BitBoxSwiss/bitbox02-api-go v0.0.0-20240925080402-a2115fee878e
-	github.com/BitBoxSwiss/block-client-go v0.0.0-20240516081043-0d604acd6519
+	github.com/BitBoxSwiss/block-client-go v0.0.0-20241009081439-924dde98b9c1
 	github.com/btcsuite/btcd v0.24.2
 	github.com/btcsuite/btcd/btcec/v2 v2.3.4
 	github.com/btcsuite/btcd/btcutil v1.1.6

go.sum

@@ -1,7 +1,7 @@
 github.com/BitBoxSwiss/bitbox02-api-go v0.0.0-20240925080402-a2115fee878e h1:wEIIFhiZ58RsVjoKfwSBBD0i75uZ7KATOI/elaBWOOY=
 github.com/BitBoxSwiss/bitbox02-api-go v0.0.0-20240925080402-a2115fee878e/go.mod h1:Spf6hQRSylrvdjd7Cv4Tc8rFwlcamJAC8EuA61ARy7U=
-github.com/BitBoxSwiss/block-client-go v0.0.0-20240516081043-0d604acd6519 h1:diVA/i8TJFBl9ZyMNX15KjZBpI2Gu63xQTozu6FsTrA=
-github.com/BitBoxSwiss/block-client-go v0.0.0-20240516081043-0d604acd6519/go.mod h1:SJTiQZU9ggBzVKMni97rpNS9GddPKErndFXNSDrfEGc=
+github.com/BitBoxSwiss/block-client-go v0.0.0-20241009081439-924dde98b9c1 h1:5hjP8mYSVKFibesrz8L6U0Vp5zSJt0LwXB3DSZGhnSo=
+github.com/BitBoxSwiss/block-client-go v0.0.0-20241009081439-924dde98b9c1/go.mod h1:SJTiQZU9ggBzVKMni97rpNS9GddPKErndFXNSDrfEGc=
 github.com/DataDog/zstd v1.4.5 h1:EndNeuB0l9syBZhut0wns3gV1hL8zX8LIu6ZiVHWLIQ=
 github.com/DataDog/zstd v1.4.5/go.mod h1:1jcaCB/ufaK+sKp1NBhlGmpz41jOoPQ35bpF36t7BBo=
 github.com/Microsoft/go-winio v0.6.2 h1:F2VQgta7ecxGYO8k3ZZz3RS8fVIXVxONVUPlNERoyfY=